Appendix G. Regular Expressions

^

Match the beginning of a string.

mysql> SELECT 'fo\nfo' REGEXP '^fo$';                   -> 0
mysql> SELECT 'fofo' REGEXP '^fo';                      -> 1

$

Match the end of a string.

mysql> SELECT 'fo\no' REGEXP '^fo\no$';                 -> 1
mysql> SELECT 'fo\no' REGEXP '^fo$';                    -> 0

.

Match any character (including carriage return and newline).

mysql> SELECT 'fofo' REGEXP '^f.*$';                    -> 1
mysql> SELECT 'fo\r\nfo' REGEXP '^f.*$';                -> 1

a*

Match any sequence of zero or more a characters.

mysql> SELECT 'Ban' REGEXP '^Ba*n';                     -> 1
mysql> SELECT 'Baaan' REGEXP '^Ba*n';                   -> 1
mysql> SELECT 'Bn' REGEXP '^Ba*n';                      -> 1

a+

Match any sequence of one or more a characters.

mysql> SELECT 'Ban' REGEXP '^Ba+n';                     -> 1
mysql> SELECT 'Bn' REGEXP '^Ba+n';                      -> 0

a?

Match either zero or one a character.

mysql> SELECT 'Bn' REGEXP '^Ba?n';                      -> 1
mysql> SELECT 'Ban' REGEXP '^Ba?n';                     -> 1
mysql> SELECT 'Baan' REGEXP '^Ba?n';                    -> 0

de|abc

Match either of the sequences de or abc.

mysql> SELECT 'pi' REGEXP 'pi|apa';                     -> 1
mysql> SELECT 'axe' REGEXP 'pi|apa';                    -> 0
mysql> SELECT 'apa' REGEXP 'pi|apa';                    -> 1
mysql> SELECT 'apa' REGEXP '^(pi|apa)$';                -> 1
mysql> SELECT 'pi' REGEXP '^(pi|apa)$';                 -> 1
mysql> SELECT 'pix' REGEXP '^(pi|apa)$';                -> 0

(abc)*

Match zero or more instances of the sequence abc.

mysql> SELECT 'pi' REGEXP '^(pi)*$';                    -> 1
mysql> SELECT 'pip' REGEXP '^(pi)*$';                   -> 0
mysql> SELECT 'pipi' REGEXP '^(pi)*$';                  -> 1

{1}, {2,3}

{n} or {m,n} notation provides a more general way of writing regular expressions that match many occurrences of the previous atom (or “piece”) of the pattern. m and n are integers.

To be more precise, a{n} matches exactly n instances of a. a{n,} matches n or more instances of a. a{m,n} matches m through n instances of a, inclusive.

m and n must be in the range from 0 to RE_DUP_MAX (default 255), inclusive. If both m and n are given, m must be less than or equal to n.

mysql> SELECT 'abcde' REGEXP 'a[bcd]{2}e';              -> 0
mysql> SELECT 'abcde' REGEXP 'a[bcd]{3}e';              -> 1
mysql> SELECT 'abcde' REGEXP 'a[bcd]{1,10}e';           -> 1

[a-dX], [^a-dX]

Matches any character that is (or is not, if ^ is used) either a, b, c, d or X. A - character between two other characters forms a range that matches all characters from the first character to the second. For example, [0-9] matches any decimal digit. To include a literal ] character, it must immediately follow the opening bracket [. To include a literal - character, it must be written first or last. Any character that does not have a defined special meaning inside a [] pair matches only itself.

mysql> SELECT 'aXbc' REGEXP '[a-dXYZ]';                 -> 1
mysql> SELECT 'aXbc' REGEXP '^[a-dXYZ]$';               -> 0
mysql> SELECT 'aXbc' REGEXP '^[a-dXYZ]+$';              -> 1
mysql> SELECT 'aXbc' REGEXP '^[^a-dXYZ]+$';             -> 0
mysql> SELECT 'gheis' REGEXP '^[^a-dXYZ]+$';            -> 1
mysql> SELECT 'gheisa' REGEXP '^[^a-dXYZ]+$';           -> 0

[.characters.]

Within a bracket expression (written using [ and ]), matches the sequence of characters of that collating element. characters is either a single character or a character name like newline. You can find the full list of character names in the regexp/cname.h file.

mysql> SELECT '~' REGEXP '[[.~.]]';                     -> 1
mysql> SELECT '~' REGEXP '[[.tilde.]]';                 -> 1

[=character_class=]

Within a bracket expression (written using [ and ]), [=character_class=] represents an equivalence class. It matches all characters with the same collation value, including itself. For example, if o and (+) are the members of an equivalence class, then [[=o=]], [[=(+)=]], and [o(+)] are all synonymous. An equivalence class may not be used as an endpoint of a range.

[:character_class:]

Within a bracket expression (written using [ and ]), [:character_class:] represents a character class that matches all characters belonging to that class. The following table lists the standard class names. These names stand for the character classes defined in the ctype(3) manual page. A particular locale may provide other class names. A character class may not be used as an endpoint of a range.

mysql> SELECT 'justalnums' REGEXP '[[:alnum:]]+';       -> 1
mysql> SELECT '!!' REGEXP '[[:alnum:]]+';               -> 0

[[:<:]], [[:>:]]

These markers stand for word boundaries. They match the beginning and end of words, respectively. A word is a sequence of word characters that is not preceded by or followed by word characters. A word character is an alphanumeric character in the alnum class or an underscore (_).

mysql> SELECT 'a word a' REGEXP '[[:<:]]word[[:>:]]';   -> 1
mysql> SELECT 'a xword a' REGEXP '[[:<:]]word[[:>:]]';  -> 0